1. Field of the Invention
This invention relates in general to well tools and methods for making and breaking threaded connections in a well pipe. In particular, the invention relates to a device which will jump the upper pipe section out of the connection, when the connection has been unthreaded, and will guide the upper pipe section during a stabbing operation.
2. Description of the Prior Art
This invention is basically an improvement of the device and method described in U.S. Pat. No. 4,348,920 (Boyadjieff), issued Sept. 14, 1982. That device is a power driven tool for making and breaking threaded connections between well pipe sections. The tool includes a movable carriage, a well pipe spinner, and a torque wrench assembly. The torque wrench assembly consists of a pair of wrenches, which are used to make and break connections between the tool joints on upper and lower pipe sections. The spinner is used to rotate the upper pipe section rapidly into or out of connection with the lower pipe section.
The upper pipe section may be part of a pipe stand consisting of two or more pipe sections. During making or breaking operations, the pipe stand is usually supported by an elevator, which is suspended from a derrick hook. The hook has a biasing device, such as a spring, for jumping the upper pipe section out of the connection, once the connection has been completely unthreaded. However, there are some situations, such as on offshore drilling rigs, where the hook is not sufficient to jump the pipe stand out of the connection. On offshore rigs, the motion compensator is inactive while a connection is being made up or broken at the rotary table, so the stand jumper must contend with the acceleration forces on the stand due to heave. Another situation in which a hook is insufficient is when drill collar stands are being disconnected, because drill collar stands are much heavier than drill pipe.
The spinner described in U.S. Pat. No. 4,348,920 (Boyadjieff), is mounted on springs to compensate for the vertical movement of the upper pipe section as the upper pipe section is threaded into or out of the lower pipe section. The springs are not, however, strong enough to jump the upper pipe section out of the connection. The springs are only strong enough to counterbalance or support the weight of the spinner.